Silicon dioxide is one of the primary materials used in integrated circuit production. Silicon dioxide films are used for interlayer dielectrics and gate oxides for transistors and are presently either grown by thermal oxidation of silicon or deposited by thermal- or plasma-enhanced, chemical vapor deposition. Plasma-enhanced, chemical vapor deposition (PECVD) is often preferred since deposition temperatures are considerably lower than other methods.
The use of silane to deposit silicon dioxide films has been studied in detail. However, PECVD of silicon dioxide using tetraethoxysilane (TEOS) has been found to have several advantages over silane-based CVD processes. Although higher deposition rates are achieved with silane, better conformal coverage of a device is obtained with TEOS due to its lower reactive sticking probability on surfaces (0.045 compared to 0.35 for silane). In addition, TEOS is less hazardous and easier to handle when compared with silane. With the increasing importance of smaller features, step coverage has become an important issue as well. Thus, TEOS has become the primary material for multilevel interconnects in very large-scale, integrated circuit (VLSI) applications. Thermal CVD of silicon dioxide is often carried out with TEOS and ozone. In this process, the deposition is believed to result from the reaction of TEOS and O or O.sub.3 in the gas phase. The atomic oxygen is maintained by the decomposition of O.sub.3. Plasma-enhanced, chemical vapor deposition of SiO.sub.2 is currently performed using TEOS and a reactive oxygen source which contains O atoms or O.sub.2.sup.+ ions.
Conventional, low-pressure plasma discharges produce ions and atomic species which may damage underlying layers during the film deposition process. Since atmospheric operation offers certain advantages over vacuum processes, it was decided to explore whether the plasma jet could be used for PECVD of SiO.sub.2.
Accordingly, it is an object of the present invention to generate an intense flux of metastable and/or atomic species for use in plasma-enhanced, chemical vapor deposition onto a substrate without exposing the substrate to a significant flux of ionic species.
Another object of the invention is to generate an intense flux of metastable and/or atomic species for use in plasma-enhanced, chemical vapor deposition onto a substrate at atmospheric pressure.
Yet another object of the present invention is to generate an intense flux of metastable and/or atomic species for use in plasma-enhanced, chemical vapor deposition onto a substrate at atmospheric pressure without significantly heating the substrate with the plasma.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.